A.The rescue operations have not been very effective.
B.More than 300 injured passengers were hospitalized.
C.The cause of the tragic accident remains unknown.
D.The exact casualty figures are not yet available.
第7题
采用钻爆法掘进的岩石巷道,应当采用()。
A.预裂爆破
B.浅孔爆破
C.深孔爆破
D.光面爆破
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